It's simple to use just make sure the subtitle file is in the same folder as the avi file and this is the important bit, make sure it's named EXACTLY as the avi file eg mymovie.avi would need mymove.srt, Mymovie.srt would not work

Then just import the avi into the program and run it.

Another feature with this program is that it will also put chapters into your avi and also a tiltle page if you want.